1. Field of the Invention
The present invention pertains to improvements in wheelchairs and especially to wheelchairs in which there are removable arms capable of being easily removed by the occupant.
2. Description of the Prior Art
The construction of wheelchairs has not undergone significant changes for some time, and people who find it necessary to use a wheelchair have simply gone along with the prevailing construction and accepted whatever was available. A particularly troublesome feature in a wheelchair is the difficulty encountered in removing the arm. There are problems due to conflicting requirements for a removable arm that can be inserted in operative positions easily and one that will fit any identical model wheelchair without alteration, without having losseness or play in a side direction. It is known that the arm should be substantially free from sideward motion and be secure enough to allow a patient to apply the full weight on the arm when making a transfer. It has been the prevailing practice to design the internal dimension of the arm receiving socket and the outside dimension of the arm insert tubes to very close tolerances in order to avoid sideward give or wobble. In order to accomplish the close tolerance between socket and insert tubes it is necessary to hold the centerline dimension between sockets on the chair frame and the centerline distance between arm insert tubes to an almost perfect match. This is a difficult thing to achieve and to obtain interchangeability of arms between different chairs. A further difficulty is that if the perfect fit is achieved it requires the arm insert tubes to be inserted evenly in the sockets so that there is no jam in either socket due to tilting of the arm so the insert tubes and sockets are out of line. The several requirements in the fit of an arm to a wheelchair side frame make it very difficult to reach an accuracy greater than present manufacturing techniques can guarantee.
One example of removable arms for wheelchairs is exemplificed by Offner U.S. Pat. No. 3,140,119 of July 7, 1964 where the arm insert tubes have polygonal feet to be received in round sockets. Another example is Fox U.S. Pat. No. 3,244,453 of Apr. 5, 1966 which shows the provision of round stems on the arm insert members received in round sockets. Yet another example is seen in Kernes U.S. Pat No. 3,376,065 of Apr. 2, 1968 where a single square insert and square socket are adapted to locate an arm and prevent arm rotation.